NASA's Mars Observer was designed to conduct a high-resolution photography mission of the Red Planet. Just two days prior to planned entry into Mars orbit, the spacecraft stopped sending telemetry as planned but was never heard from again.
Sept. 25, 1992: Launch
Aug. 22, 1993: Spacecraft stopped sending telemetry and was never heard from again
Mars Observer was designed to carry out a high-resolution photography mission of the Red Planet over the course of a Martian year (687 days) from a 235 × 217-mile (378 × 350-kilometer) polar orbit.
Building on the research done by the Viking missions, it carried a suite of instruments to investigate Martian geology, atmosphere, and climate in order to fill in gaps in our knowledge of planetary evolution.
A mere 31 minutes after launch, the new transfer orbit stage (TOS), using the Orbus 21 solid rocket motor, fired to boost the spacecraft on an encounter trajectory with Mars.
After a 450 million-mile (725 million-kilometer) voyage lasting nearly 11 months, at 00:40 UT Aug. 22, 1993—just two days prior to planned entry into Mars orbit—the spacecraft stopped sending telemetry as planned, but then never resumed sending data 14 minutes later as expected.
Despite vigorous efforts to regain contact, Mars Observer remained quiet.
When the spacecraft did not re-establish contact after five days of silence, mission planners finally gave up hope on salvaging the mission.
The results of a five-month investigation proved to be inconclusive, but one likely cause of the catastrophic failure may have been a fuel line rupture that could have damaged the spacecraft’s electronics, throwing the vehicle into a spin.
In addition, the fact that the Mars Observer bus was a repurposed Earth science satellite bus may have also compromised the spacecraft’s ability to adapt to the deep space environment.
While none of the primary mission objectives was accomplished, the spacecraft did return data during its interplanetary cruise.
Scientific instruments developed for Mars Observer were later used on several subsequent Mars probes, including Mars Global Surveyor (launched in 1996), Mars Climate Orbiter (1998), Mars Odyssey (2001), and Mars Reconnaissance Orbiter (2005).